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techtalk:ih:oil03c [2018/12/19 17:11]
hippysmack [77-85 Oil Pump Damage Pics]
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-====== IH: Oiling & Lubrication - Sub-03A ====== 
-====== 77-85 Oil Pump Damage and Repair ====== 
-====== Cracks in Housing or Cover ====== 
  
-This cover was cracked at the oil pressure switch end. \\  
-The crack was welded over and a Dremil tool was used to reshape the cover. \\ 
-Due to warpage during welding, the threads need to be chased with a tap to straighten them back out. \\ 
-|  Repair on oil pump cover ((photos by Farmer00-1 of the XLFORUM http://​xlforum.net/​forums/​showthread.php?​t=554323)) ​ || 
-|{{:​techtalk:​ih:​oil:​cracked_oil_pump_cover_1_by_acb2.jpg?​direct&​300|}}|{{:​techtalk:​ih:​oil:​cracked_oil_pump_cover_2_by_acb2.jpg?​direct&​300|}}| 
-====== Scratches on Gerotors or Mating Surfaces ====== 
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-  * Many used oil pumps have scratches on both the gerotors and pump surfaces that the gerotors ride on. 
-  * But, there is one certain spot that seems to be scratched more times than others. ((Hippysmack of the XLFORUM http://​xlforum.net/​forums/​showthread.php?​t=2071153&​page=6)) 
-    * It's on the larger of the two pads in the pump body and the cover seem to usually have more wear. 
-    * Sometimes, the small pad is scratched or damaged also but not always. 
-    * The gap between the inner and outer gerotors on both the feed and return sides tends to be scratched as in the pics below. 
-    * Debris caught between these two gears cannot slide over and fall to the other cavity and out of the pump. 
-    * It gets locked between the gears and ripped across the aluminum surface. 
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-|{{:​techtalk:​ih:​oil:​77-85_oil_pump_cover_11_by_hippysmack.jpg?​direct&​500|}}|{{:​techtalk:​ih:​oil:​77-85_oil_pump_cover_12_by_hippysmack.jpg?​direct&​500|}}| 
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-|{{:​techtalk:​ih:​oil:​77-85_oil_pump_cover_7_by_hippysmack.jpg?​direct&​500|}}|{{:​techtalk:​ih:​oil:​77-85_oil_pump_cover_8_by_hippysmack.jpg?​direct&​500|}}| 
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-  * In theory, no particles of any size should be able to spin around to the small pad due to the pressure generated by the spring washer and the gerotor spacing there. 
-  * Also, any debris picked up from the source side cavity should drop down into the feed side cavity and out of the pump. 
-  * The side toward the motor is where oil is transferred to and from the pump. 
-  * The inner and outer gears come together on the other side (right side). 
-  * This spacing relationship doesn'​t change between the motor side or the outside of the pump due to the offset gearshaft. 
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-  * But in reality, debris gets caught in or between the gears and gets dragged over the aluminum flats. 
-    * Some then find their way under the gerotors while the spring washer flexes from the stress. 
-    * The debris spins around under the gerotors and wears scratches in the flats (pads) or worse. 
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-|{{:​techtalk:​ih:​oil:​77-85_oil_pump_cover_9a_by_hippysmack.jpg?​direct&​500|}}|{{:​techtalk:​ih:​oil:​77-85_oil_pump_cover_10a_by_hippysmack.jpg?​direct&​500|}}| 
-|  Gerotor rotation ((photos by Hippysmack http://​xlforum.net/​forums/​showthread.php?​t=2071153&​page=6)) ​ || 
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-|{{:​techtalk:​ih:​oil:​83_oil_pump_by_sc72.jpg?​direct&​300|}}|{{:​techtalk:​ih:​oil:​77_oil_pump_gearshaft_pin_broke_by_77_iron.jpg?​direct&​500|}}| 
-|  Oil pump from an 83 model ((photo by sc72 of the XLFORUM http://​xlforum.net/​forums/​showthread.php?​t=1717592&​page=15)) ​ |  Gearshaft pin broke off into this 77 model ((photo by 77 iron of the XLFORUM http://​xlforum.net/​forums/​showthread.php?​t=1831941&​page=2)) ​ | 
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-  * There should be some reduced pressure because of the scratches. 
-  * Pressure generated to the output cavity can squirt back to the input side through these scratches. 
-  * How much pressure loss would depend on the width, depth, length of the scratches and oil viscosity. 
-  * To make the pump inoperative or not make pressure (from the scratches alone); 
-    * The scratches would have to be proportional to the relative volume of all four gerotor reservoirs combined. 
-    * Then, the check valve would have to accept less pressure flow than the backpressure from the pump. 
-  * The gerotor surface in the cover would have to be eat up pretty bad to make the pump completely ineffective. 
-  * The pump would have less pressure loss with multi-weight or straight weight oil when cold than hot. 
-  * They'​ll both flow faster when hot. 
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